The invention is in the chemical arts. It relates to clays, the particles of which are water swellable, the intercalation and exfoliation of such particles, and synthetic resin compositions comprising the exfoliated particles.
Clays are silicate minerals, the particles of which have equivalent spherical diameters of less than 2 xcexcm. For many years clay has been used in synthetic resin compositions (in more common terminology, polymer compositions) to enhance or impart toughness, heat deflection temperature, oxygen barrier and optical properties of or to the compositions. Such use has led to the development of nanocomposites. These are compositions that comprise normally solid, polymer material and, highly dispersed in the matrices of the polymer material, diminuted clay particles. These particles are in the form of platelets, the thicknesses of which are measured in nanometers. Diminuted clay particles of such fineness are obtained from water swellable clays which include crystalline clays that belong to the class of layer silicates, also referred to as phyllosilicates. The phyllosilicates include the smectite (or montmorillonite), mica and vermiculite groups of clays. The particles of these minerals are formed by layers or laminates of crystalline silicate platelets. The layers are strongly held together by electrochemical attraction. When these minerals are exposed to water, it diffuses into the particles between the layers, and causes the layers to move apart, (as evidenced by expansion or swelling of the particles), whereby the layers are not as strongly held together. When these minerals are subjected to drying conditions, water between the layers escapes and evaporates, and the particles shrink.
One method of obtaining the diminuted clay particles is based on this water swelling effect. In the method, an aqueous solution or dispersion of an organoelectrolyte, and water swellable clay such as a phyllosilicate are admixed. The solution or dispersion migrates into the phyllosilicate particles between the layers, and forces the layers apart. Water is evaporated from the particles. However, because of the electrolytic portion of the organoelectrolyte, it remains between the layers of silicate platelets, and because of the bulk of the organo portion, the layers remain spaced apart. The resulting swollen particles are described as intercalated, and the organoelectrolyte is referred as the intercalant. In such condition substantially less shear is needed to separate the platelet layers from each other. Sufficient shear is applied to the intercalated particles to overcome the forces holding the layers together, and delaminate them, whereby diminuted clay particles are obtained. Such particles are referred to as exfoliated clay particles. In most instances, the shear involved in the melt blending of the polymer material and the intercalated, phyllosilicate particles is sufficient to exfoliate the particles.
There are numerous patent and other publications relating to nanocomposites, how to make them, and the preparation of intercalated clays for use in making nanocomposites. Representative of such publications is the U.S. Pat. No. 5,552,469 to Beall et al. This patent discloses nanocomposites in which examples of the matrix polymers (from which the normally solid polymer material of the patent is selected) comprise such homopolymers as polyethylene and polypropylene, and such copolymers as propylene copolymers and ethylene copolymers with ethylene-propylene copolymers and ethylene-propylene-diene terpolymers being mentioned. The clay disclosed in the patent is a phyllosilicate such as a smectite clay and the intercalant disclosed in the patent includes an oligomer with carbonyl, hydroxyl, carboxyl, amine and/or ether functionalities.
The invention comprises a clay material intercalated with intercalant material comprising an organic compound having a nonpolar portion bonded to a polar portion. The nonpolar portion for the most part is a saturated oligomer of isoprene. It resembles or mimics the basic structure or parts of the basic structure of the hydrocarbon backbone of homopolymers and copolymers of propylene and of ethylene. This portion, therefore, tends to be compatible with such polymers, especially copolymers of both propylene and ethylene. The polar portion tends to have an affinity for the silicate platelets of the clay material. Consequently, the organic compound enhances the compatibility with such polymers of the exfoliated, clay material that results when melt blending, with sufficient shear to exfoliate the intercalated clay material, the polymers and the clay material intercalated with the intercalant material.
The invention further comprises a nanocomposite containing a C2-C3 xcex1-olefin polymer material and dispersed in the matrix thereof an exfoliated, clay material that before exfoliation had been intercalated with intercalant material comprising the foregoing organic compound. The C2-C3 xcex1-olefin polymer material is material selected from the group consisting of homopolymers of propylene and ethylene, xcex1-olefin copolymers in which polymerized propylene units predominate, xcex1-olefin copolymers in which polymerized ethylene units predominate, copolymers of propylene and ethylene or propylene and butene-1 in which the polymerized propylene and ethylene units or propylene and butene-1 are substantially equal in number and together predominate, the latter copolymers of propylene and ethylene or propylene and butene-1 being with or without other different polymerized C4-C10 xcex1-olefin units, and mixtures thereof
In the more specific aspects of the invention, the essential component of the intercalant material, that is, the above mentioned organic compound, has the general formula: 
in which R is H or a normal or branched C1-C4 alkyl, n is 2-17, and Rxe2x80x2 is a radical with at least one polar group or moiety. In most embodiments of the compound, Rxe2x80x2 is X, COORxe2x80x3, CN, NRxe2x80x3xe2x80x22 or NRxe2x80x3xe2x80x22xc2x7HX with Rxe2x80x3 being Rxe2x80x3xe2x80x2, NRxe2x80x3xe2x80x22, NRxe2x80x3xe2x80x22xc2x7HX or a monovalent metal cation, Rxe2x80x3xe2x80x2 being H or a normal or branched C1-C4 alkyl and X being I, Br, Cl or F. In each of NRxe2x80x3xe2x80x22 or NRxe2x80x3xe2x80x22xc2x7HX, each Rxe2x80x3xe2x80x2 can be the same or different. However, in preferred embodiments, Rxe2x80x3 is NHRxe2x80x3xe2x80x2xc2x7HX. Examples of a normal or branched C1-C4 alkyl are methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl and tert-butyl. Examples of a monovalent metal cation include cations of an alkali metal in Group 1A of the Periodic Table of the Elements (e.g., Li, Na, and K).
One way to make the generic compound comprises condensing isoprene anionically with a C1-C4 alkyllithium to form an oligomer of 3-18 isoprenoid units with C1-C4 alkyl being a substituent of a methyl carbon of the end isopropyl group of the unsaturated hydrocarbon backbone, and with lithium being an ionically attached to the methylene carbon at the other end of the backbone. The oligomer is reacted with either ethylene oxide or carbon dioxide, and then with water, to replace the lithium ion with a hydroxyethyl group or a carboxyl group. In either case the resulting compound is hydrogenated over a Pt or Rh catalyst to saturate the backbone. The hydrogenation reaction is typically done at 35 to 40xc2x0 C. in hexane for 8-12 hours.
The saturated, hydroxyethyl substituted compound is halogenated with a hydrogen halide (hydrogen bromide or iodide being preferred because of the ease of reaction) to form a compound of the formula in which Rxe2x80x2 is X. This halide compound is reacted with (1) an alkali metal cyanide to obtain a compound in which Rxe2x80x2 is CN, and (2) ammonia (or ammonium hydroxide), or a mono- or di(C1-C4alkyl)amine to obtain a compound in which Rxe2x80x2 is NRxe2x80x3xe2x80x22. The latter compound is reacted with a hydrogen halide to obtain a compound in which Rxe2x80x2 is NRxe2x80x3xe2x80x22xc2x7HX. The saturated, carboxy substituted compound is reacted with (1) a C1-C4 alcohol to form the compound, an ester, in which Rxe2x80x3 is C1-C4 alkyl, (2) ammonia (or ammonium hydroxide), or a mono- or di(C1-C4alkyl)amine to obtain a compound in which Rxe2x80x3 is NRxe2x80x3xe2x80x22, and (3) an alkali metal base to give a compound in which Rxe2x80x3 is a monovalent metal (alkali metal) cation. Similar to the above, the aminocarboxymethyl compound (in which Rxe2x80x3 is NRxe2x80x3xe2x80x22) is reacted with a hydrogen halide to obtain a compound in which Rxe2x80x3 is NRxe2x80x3xe2x80x22xc2x7HX. All of the reactions described in this paragraph are conventional type reactions, and the general conditions thereof are well known to organic chemists of ordinary skill in the art.
A highly preferred embodiment of the compound, and a precursor of other embodiments of the compound is 3,7,11-trimethyldodecyl halide. A process for making the embodiment starts with 3,7,11-trimethyldodecatriene-1-ol, a naturally occurring isoprenoid known as farnesol. In the process this chemical is catalytically hydrogenated to 3,7,11-trimethyldodecan-1-ol which in turn is halogenated. The resulting halide is reacted as above indicated with respect to the generic halide compound to obtain the various other Rxe2x80x2 radicals. Thus, the resulting halide is reacted with a C1-C4 alkyl amine to form C1-C4 alkyl (3,7,11-trimethydodecyl) amine. This amine compound then is reacted with a hydrogen halide to form the quaternary compound 3,7,11-trimethyldodecylamine hydrohalide. This quaternary ammonium compound is a preferred compound because of its higher affinity, compared to the other, non-quaternary ammonium embodiments of the generic compound, with phyllosilicates, especially semectites.
As above stated, the generic compound has a general affinity for silicate platelets such as those in phyllosilicates, and general compatibility with C2-C3 xcex1-olefin polymer material. However, the degree of affinity for the silicate platelets varies from one specific embodiment of the compound to another, depending to a large extent on the composition of the platelets and the degree of polarity of Rxe2x80x2. Similarly, the degree of compatibility with the polymer material varies from one specific embodiment of the compound to another, depending to a large extent on the value of n in the formula. Nevertheless, in each case there is significant enhancement of the compatibility of the silicate platelets with the polymer material when the generic compound is combined with the platelets. In addition, the generic compound tends to be in melted condition at the same temperatures at which such polymer material is molten, and this has a favorable effect on compatibility when the intercalated clay particles are admixed with the polymer material in the melted condition, and under sufficient shear to exfoliate the particles.
In some embodiments of the invention the intercalant material comprises only one compound within the scope of the above general formula. In other embodiments it comprises more than one such compound. These other embodiments are typical when intercalant material is made from isoprene.
In all embodiments of the invention substantially all of the clay material is water swellable. In some of these embodiments the clay material comprises only one variety of water swellable clay. In other embodiments it comprises more than one such variety. These embodiments include those having clay in one group of the phyllosilicate class (for example, the smectite group), and another clay in another group of the class (for example, the vermiculite group), and embodiments in which all the clays are in one phyllosilicate group. In the more preferred embodiments the clay or clays is or are in the smectite group.
The intercalated, clay material of this invention is made by preparing an aqueous solution or suspension of the intercalant material, admixing water swellable clay material and the solution or suspension, and, when enough of the solution or suspension has infiltrated and been sorbed by the clay material to substantially swell the particles thereof, the thus intercalated clay material is separated from the aqueous solution or suspension and dried.
In the preparation of an aqueous solution or suspension of intercalant material, the amount of intercalant material admixed with the liquid generally is such that the concentration of the material in the solution or suspension is about 10-50 parts by weight of the solution or suspension. Solubility of the intercalant material in water is dependent for the most part on the carbon chain length or lengths (i.e., the absolute or average value of n in the general formula) and to a lesser extent on the degree of polarity or polarities of the polar portion or portions of the compound or compounds The shorter the chain lengths (the smaller the value of n, e.g., from 2 to 10), the greater is the solubility. The more polar the polar portion, the greater is the solubility. The optimum chain length for compatibility of the compound or compounds of the intercalant material with C2-C3 xcex1-olefin polymer material appears to exist when the absolute or average value of n is 12. At the absolute or average chain length corresponding to this number, the solubility of the intercalant material in water might only be partial. In such case a water-miscible solvent for the compound, for example, a C1-C4 alcohol (methanol, ethanol, and the like) can be part of the liquid medium. The concentration of the water-miscible solvent should be sufficient so that at least an easily stirrable suspension of the intercalant material is formed when the material is admixed with the water-solvent solution. This preparation of the aqueous solution or suspension normally is carried out at 20-25xc2x0 C. and atmospheric pressure. However, operable higher and lower temperatures and pressures are within the broader concepts of the invention.
The relative amounts of the solution or suspension admixed with the water swellable clay material can vary. However, satisfactory results are obtained when the amounts are such that the weight ratio of intercalant material to the clay material is generally about 20:100-40:100, and preferably about 27:100-32:100.
The period of time the water swellable clay material is in contact with the aqueous solution or suspension is dependent on the rate of infiltration or migration of the solution or suspension into and its sorption by the clay material. This in turn is dependent on the clay or clays that make up the clay material. Preferably, the period should be sufficient to achieve maximum or substantially maximum swelling of the clay particles. To determine the period, test runs, which can be readily done, are recommended. However, a period of time of generally about 1-12 hours and preferably about 6-8 hours gives satisfactory results.
These steps of the preparation of the intercalated, clay material are performed in conventional equipment.
As to the nanocomposite of this invention, the concentration of the exfoliated, intercalated clay material component thereof is dependent on the desired physical properties of the articles made therefrom. However, in general the concentration is about 2-25 parts by weight of the nanocomposite, and preferably about 5-15 parts by weight of the nanocomposite.
While the essential components of the nanocomposite are C2-C3 xcex1-polymer material and the exfoliated, intercalated clay material of this invention, specific embodiments of the nanocomposite include at least one other additional component. That additional component is antidegradant material (material selected from antioxidants, heat stabilizers, and the like). Other additional components include material selected from the group comprising antacids, colorants, compatibilizers other than the intercalant material of this invention, and the like, including other substances not here listed, but conventionally in nanocomposites.
The nanocomposite of this invention is made by melt blending C2-C3 xcex1-olefin polymer material, the intercalated clay material of this invention, preferably antidegradant material, and such other components as might be involved in the embodiment being made. In this regard, one of the general embodiments of the nanocomposite is a concentrate or masterbatch, and in specific embodiments thereof one or more of such other components are not included until the concentrate and such other components are melt blended with additional C2-C3 xcex1-olefin polymer material to make the ultimate polymer composition for forming useful articles.
The melt blending of at least the C2-C3 xcex1-olefin polymer material and the intercalated clay material of this invention is done by conventional ways and means. In doing so, the shear applied to achieve a uniform blend usually is sufficient to exfoliate the intercalated clay material and, with the aid of the intercalant material, distribute the resulting exfoliated platelets uniformly throughout the melted C2-C3 xcex1-olefin polymer material.
After the nanocomposite of this invention is made and still is in the molten condition, it can be used as is to manufacture by conventional ways and means useful solid articles or solid pellets for later manufacture of useful articles.